7-[2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3-vinyl-3-cephem-4-carboxylic acid (syn isomer), known as Cefdinir, is a cephalosporin antibiotic having high antibiotic activity and broad antibacterial spectrum. Cefdinir was first disclosed in U.S. Pat. No. 4,559,334, which is incorporated herein by reference.
To date, two crystal forms of Cefdinir have been observed and prepared in view of suitability for a pharmaceutical product and ease for handling. One crystal form of Cefdinir (hereinafter referred to as “crystal form A”) has been disclosed in, for example, U.S. Pat. No. 4,935,507, incorporated herein by reference, which has been widely used as an oral pharmaceutical suspension form.
Another crystal form of Cefdinir (monohydrate, also referred to as “crystal form B”) including its method of preparation has been disclosed in JP Patent application No. 62-206199 found in the file of EP0304019, which is incorporated herein by reference. Recently, crystal form B has also been described in US 2003/0204082 A1. However, crystal form B of Cefdinir has not been used to form oral suspensions.